[llvm] [llvm-ar] fix inconsistent case sensitivity for path matching on Windows (PR #196541)

[Ben Dunbobbin via llvm-commits]

bd1976bris wrote:

> > @bd1976bris This only affects behavior with -N. The behavior in your scenario remains unchanged:
> > ```powershell
> > PS C:\Users\user\llvm-project\temp> Set-Alias llvm-ar ..\build\Debug\bin\llvm-ar.exe
> > ...
> > ```
> 
> Thanks. So, just to spell this out, the only way that I can see this affecting existing builds is in a scenario analogous to the following:
> 
> ```
> > echo foo  1>foo.txt
> > llvm-ar.exe q foo.a foo.txt
> llvm-ar.exe: warning: creating foo.a
> > del foo.txt
> > echo FOO >FOO.txt
> > llvm-ar.exe q foo.a FOO.txt
> > del foo.txt
> > echo foo2 >foo.txt
> > llvm-ar.exe q foo.a foo.txt
> > del foo.txt
> > llvm-ar.exe t foo.a
> foo.txt
> FOO.txt
> foo.txt
> ```
> 
> With the current llvm-ar we would get:
> 
> ```
> > llvm-ar.exe xN 2 foo.a foo.txt
> > type foo.txt
> foo2
> ```
> 
> Whereas with this patch we would get:
> 
> ```
> > llvm-ar.exe xN 2 foo.a foo.txt
> > type foo.txt
> FOO
> ```
> 
> I think this is unlikely to occur. I'll try to establish if that's true.



https://github.com/llvm/llvm-project/pull/196541